The present invention relates to a semiconductor integrated circuit device having a trimming circuit and non-volatile memory elements, and more particularly to a semiconductor integrated circuit device capable of calibration in which the circuit device memorizes timing data in the non-volatile memory elements, then reads out the memorized data from the non-volatile memory elements, and changes an operation condition based on the read out data comprising semiconductor elements.
The present invention further relates to a semiconductor integrated circuit device capable of writing data in non-volatile elements with constant stable data writing time at a voltage range from an ultra-low voltage such as less than 1.0 V to a high voltage such as more than 3.0 V.
In the prior electrically erasable programmable read only memory (hereafter, EEPROM), the configuration shown in FIG. 4 has been used as a circuit for writing data in memory elements.
Referring to the drawing, the circuit will be described.
First a writing signal is input to a timer circuit 901.
Timing of the writing operation is controlled by the timer circuit 901.
A booster circuit 902 and an address decoder 903 operate according to the timing of the timer circuit 901, and serve to write data in a non-volatile memory array 904.
A block diagram of the prior timer circuit is shown in FIG. 5.
In the operation of the timer circuit, a capacitor is included in a constant current ciruit 1001, and in the capacitor electric charge is charged by letting a constant current determined by an output voltage of a first regulated voltage circuit 1004 flow to the capacitor.
By comparing the voltage of the capacitor with the output voltage of a second regulated voltage circuit 1003 at a voltage comparing circuit 1002 for comparing voltage, a certain constant time is obtained.
In the prior timer circuit, writing time deviates between 2 ms to 8 ms depending on deviation of circuit constants and manufacturing process. Further, depending on the threshold of a transistor included in the circuit, it is difficult to make the output of the regulated voltage circuit and reference voltage of the voltage comparing circuit less than 1.0 V with a power supply voltage of less than 1.0 V. When the power supply voltage is less 1.0 V, the output voltage of the first regulated voltage circuit 1004 and the output of the second regulated voltage circuit 1003 which operates as reference voltage of the voltage comparing circuit greatly vary with power supply voltage. Therefore, it has been difficult to maintain writing time constant.
As the output voltage of the regulated voltage circuit is near the threshold voltage of a MOS transistor when power supply voltage is less than 1.0 V, current value of the constant current circuit greatly varies with a slight deviation in voltage. Because of that, writing time has greatly varied.